Danielle Weisberg, left, and Carly Zakin, co-founders of the email newsletter theSkimm.Credit Chester Higgins Jr./The New York Times

Online news start-ups have garnered buzz, and millions of dollars, over the last few years. But few can boast of vocal fans like Oprah Winfrey, especially while focusing on the least sexy of media: email.

And yet that’s what theSkimm, a daily news briefing marketed toward young women — and written with a touch of snark — has done.

Drawing on enviable growth in subscriptions and the promise of a bigger brand, the start-up announced Tuesday evening that it had raised $6.25 million in financing from a group of investors that includes the investment firms RRE, Homebrew and Greycroft Partners, the comedian Chelsea Handler and Irving Azoff, the former chief executive of Ticketmaster. Founded by Danielle Weisberg and Carly Zakin, two former associate producers at NBC News, theSkimm has grown to more than a million active readers who digest the newsletter’s informal, sometimes flip, tone. (A distillation of one of the latest allegations against Bill Cosby was headlined, “What to say when your friend wants to go to a comedy show,” followed by, “Let’s skip Bill Cosby for now.”) “For us, there was a conversational element to the news that was missing,” Ms. Zakin said.

The two founders describe themselves as news fans who had dreamed of working at NBC. (Ms. Zakin said that she grew up idolizing Katie Couric.) They said they were drawn to the needs of their nonjournalist friends who, for all their intelligence and success, could not find the time to catch up on the news. Not even social media like Facebook and Twitter appeared to fill that gap.

The solution was a simple briefing, written in the voice of their best friends, distilling the top news of the day in a compelling way. Lack of a computer programming background didn’t hurt, according to Ms. Zakin, since they still viewed email as an essential part of their target audience’s routines.

By July 2012, after four years at NBC, both women had quit their jobs and started the newsletter from their Manhattan apartment.

Though theSkimm’s approach is decidedly low-tech, it has paid dividends. The number of active readers has grown tenfold, Ms. Zakin said. The newsletter’s average open rate, or how many subscribers open the email, stands at about 45 percent. And the company now generates revenue via sponsorships from the likes of the National Basketball Association and Turner Sports. (With those partnerships came opportunities like having Paul Pierce, then of the Brooklyn Nets, and the commentator Reggie Miller deliver bite-size interviews.) Perhaps most strikingly, theSkimm has now drawn what Ms. Weisberg and Ms. Zakin call their “Skimm’bassador” program: enthusiastic subscribers who actively promote the service to their friends. Six months ago, the company counted 80 such representatives; now, the two founders said, the program’s participants number in the thousands.

And despite marketing their newsletter to women in their 20s to mid-30s — the millennial set — the start-up has drawn fans everywhere. Reese Witherspoon told Vanity Fair in September that she reads the newsletter. A month later, Oprah declared on Twitter that she had become a “Skimm’er.”

Steven Schlafman, a principal at RRE Ventures and the lead investor in the new financing round, said that the chief operating officer of another company recently gushed about the newsletter. That executive, Mr. Schlafman said, happened to be a 50-something man. “They’ve done a good job building a voice and a brand that was designed for young women, but has much more appeal,” he said.

With the new cash, theSkimm plans to expand its existing team of eight, particularly by hiring staff members who can help build new products. Ms. Weisberg and Ms. Zakin insist that their start-up can comfortably embrace multiple platforms, from video to mobile apps. Their vision, they said, is turning news into a lifestyle brand — and perhaps a next-generation “Today” show.

“Our audience is really waking up to us,” Ms. Weisberg said. “Just like previous generations woke up to morning shows.”

A version of this article appears in print on 12/17/2014, on page B7 of the NewYork edition with the headline: An Email Newsletter Draws Investors.